MITH ISLAND, Md., May 10 — "I did pretty good," said Willard Laird, lifting his day's catch of soft-shell crabs onto this pristine Colonial island, the historical settlement of some of America's original watermen. Their descendants have been working Chesapeake Bay for more than three centuries, surviving all manner of crustacean predators in the bay and passing fashions on the mainland.

"There are crabs out there, running good, and the year looks more promising," said Mr. Laird, a weather-burnished optimist sailing straight into the teeth of a warning from numerous marine scientists and Gov. Parris N. Glendening that the Chesapeake's signature blue crab fishery is "on the verge of collapse."

If it were to collapse, so might this salty sanctuary from the past whose 55 watermen still bear dialect traces of the first settlers' roots in Elizabethan England.

"For one thing, we kind of talk backward, like when we say `that ship ain't pretty' when we mean she's a beauty," said Bill Clayton, a descendant of the bay's pioneers. The past is a source of comfort for Mr. Clayton as he invokes the wisdom of the ancients that fishing cycles wax and wane in the vast Chesapeake. So it will be for the blue crab, he says, as much as for all the scientists lately pondering the bay's dwindling catch.

"We look at that water daily; the college-degree people go by things they learned in books," Mr. Clayton said. He and about 10,000 other watermen around the bay are counting on the blue crab to outwit the scientists' consensus warning, which has resulted in the political decision by Maryland and Virginia to mandate a 15 percent cut in the bay's blue crab harvest in the next three years. The step is being taken to protect the breeding stock; the catch has been steadily falling, to about 60 million pounds of crab meat annually from the high of 80 to 100 million a generation ago.

"Some of us have had to quit the water, maybe 20 in the last 10 years," said Chuck Marsh, another waterman with pioneer roots who concedes the crab fishery can be unpredictable and disappointing. But he complained far more of excessive regulation and policing, insisting the problem hardly merits harsh steps like the pending Maryland order to ban crabbing in November, cutting the season to seven months to give the fishery a chance to rebound.

As the watermen express concern for their way of life, so do scientists studying the complexities of the 64,000-square-mile bay. It is the nation's largest estuary with a surrounding population of 15 million people in six states.

"If we lost the blue crab, that island would dry up and blow away," warned Bill Goldsborough, senior scientist at the Chesapeake Bay Foundation, a private environmental watchdog agency. He noted that one by one, other bay fisheries have failed under the pressures of relentless pollution from the mainland and overfishing, with oysters, for example, "barely a shadow" of their heyday harvests.

"So it's become crabs or nothing for the watermen," Mr. Goldsborough said. "That's kind of a microcosm of the whole bay," he added. Overfishing now looms as the ultimate threat to blue crabs, and by extension to the intricate effort by science and government to repair the bay and restore its balance of species, he said.

In this mission, Mr. Goldsborough cited the watermen as "the human element of the fishery" — a prime species deserving protection as much as the hordes of "peelers" or soft-shell crabs now scuttling into the pots and scraper nets of the latest generation of Smith Islanders.

The two sides claim comfort in the fate of the rockfish, which is resurging as a fishery after nearly disappearing 20 years ago. Ubiquitous now as striped bass on East Coast menus, the rockfish had to be protected by a government ban on fishing, scientists point out. But the watermen insist that the rockfish was on its way back anyway, and that the moratorium only helped it become one of the current chief predators of the blue crab.

"My father-in-law cut open a rockfish last fall, and it had like 87 baby crabs in its gut," said Donna Smith, 38, the wife and daughter of watermen and one of the workers at the island's Ladies Crabmeat Co-op, a packing enterprise. "If you're a female on the island you either pick crabs or cut grass," she said of the 350 residents who live in three separate bay-front villages. "The life is wonderful, no crime," she added, noting that her two sons want to be watermen but that is proving an ever harder endeavor because of state regulations, costlier gear, longer hours and predators like rockfish.

But rockfish is the islanders' scapegoat, say bay scientists, who report that rockfish account for 15 to 20 percent of blue crab mortality, while watermen account for 50 percent. Among other problems, protective seabed grasses have eroded by almost 90 percent, leaving the crabs more vulnerable to predators when they need hiding places to molt. In the intricate mosaic of bay species, the more preferred diet of the rockfish, menhaden, has been fading, compounding survival pressures on the blue crab.

Not to worry, insist the watermen of Smith Island as they head out before dawn, confident they know crabs better than any scientist or politician.

"Crabs are pretty tough little animals, if you give them a chance," said Dwight Marshall, a bay fisherman who agreed some limits on crabbing seemed necessary but not the decision to ban crabbing for the month of November.

"Some of the guys will get riled," said Mr. Marshall, smiling as he suggested that finding a way around government mandates is another old island survival technique. "I'd imagine people will buck it."